The objectives of our research are the study of malignant prostatic tissue by electron microscopy using biopsies in patients undergoing different therapeutic modalities in order to determine parameters for establishing potential predictors for treatment selection and response. Procedures are followed which allow use of the same specimen for light microscopy, transmission electron microscopy and scanning electron microscopy. Diagnosis of the same specimen is done on 1 micron epon sections which are differentially stained. These procedures will be used to study serial biopsy specimens from patients treated with irradiation and/or chemotherapy. A cell line of prostatic origin (adenocarcinoma metastatic to the brain) has been established in our laboratory. Morphological studies of monolayers of these cells revealed many desmosomes, golgi vacuoles, clusters of ribosomes and abundant smooth endoplasmic reticulum. Tissue culture cells of this cell line were subcutaneously injected into nude mice. Within 2 months a tumor developed in one case. This tumor was reintroduced into tissue culture, and both the tumor and the tissue culture cells there of were studied morphologically by TEM. The ultrastructure of both was very similar to the one described above for tissue culture cells of the original tumor. Preliminary experiments have been made with the peroxidase labeling technique to explore surface antigens related to prostate adenocarcinoma. BIBLIOGRAPHIC REFERENCES: Seal, E. Jr., Mickey, D.D., and Paulson, D.F. Oncornavirus-like Protein Expression in Human Prostatic Tissue. Urological Research 4:23, 1976. Stone, K.R., Stone, M.P., and Paulson, D.F. In Vitro Cultivation of Prostatic Epithelium. Investigative Urology 14:79, 1976.